Light has a property that cannot be seen with the human eye. This property is known as polarisation, and has to do with the direction in which the fields that constitute light are oscillating.

With so-called polarisation filters, or polarisers, light can be “sorted” with a certain oscillation direction of the light wave. If the light is directed through two consecutive polarisers, the intensity of the light travelling through the filter can be regulated by turning the filter.

 This is the fundament of modern displays, for example the kind that are built into mobile phones.

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